Accessory gearbox with tower shaft removal capability

ABSTRACT

An accessory system for a gas turbine engine includes an accessory gearbox which defines an accessory gearbox axis and includes first and second sides. A first geartrain includes one or more shafts rotatable about axes perpendicular to the first side of the accessory gearbox and a second geartrain includes one or more shafts rotatable about axes perpendicular to the second side of the accessory gearbox. A driven gear set defines an input axis and drives first geartrain and the second geartrain about corresponding first and second drive axes parallel to the input axis.

This is a continuation of U.S. application Ser. No. 13/313,433 filed onDec. 7, 2011.

BACKGROUND

This disclosure generally relates to an accessory gearbox for drivingauxiliary systems of a gas turbine engine.

Aircraft powered by gas turbine engines often include a mechanicallydriven accessory gearbox to drive accessory systems such as fuel pumps,scavenge pumps, electrical generators, hydraulic pumps, etc. Thesecomponents typically operate at different speeds from one another andrequire differing amounts of horsepower as provided by the accessorygearbox.

Conventional gas turbine engine accessory gearboxes utilize a gearboxcase mountable underneath the engine. The gearbox case is typicallycrescent-shaped with forward and aft faces to which the accessorycomponents are mounted. The accessory gearbox is driven by an anglegearbox through a lay shaft which axially extends from the gearbox case.A towershaft driven by the engine high-pressure spool drives the layshaft through the angle gearbox. An ongoing issue with respect toaccessory gearboxes is the ease by which they can be serviced and/orremoved from the engine.

SUMMARY

An accessory system for a gas turbine engine according to an exemplaryembodiment of this disclosure, among other possible things, includes anaccessory gearbox which defines an accessory gearbox axis, the accessorygearbox including a first side and a second side, a first geartrainwithin the accessory gearbox including a first set of shafts rotatableabout axes perpendicular to the first side of the accessory gearbox anda second geartrain within the accessory gearbox including a second setof shafts rotatable about axes perpendicular to the second side of theaccessory gearbox. The accessory gearbox further includes a driven gearset defining an input axis, a first drive gear set driven by the drivengear set about a first drive axis for driving the first gear set, and asecond drive gear set driven by the driven gear set about a second driveaxis for driving the second gear set, wherein the first drive axis andthe second drive axis are parallel to the input axis.

In a further embodiment of the foregoing accessory system embodiment,the first drive gear set comprises a first spur gear, the second drivegear set comprises a second spur gear, and the driven gear comprises adrive spur gear driving the first and second spur gears.

In a further embodiment of any of the foregoing accessory systemembodiments, the first drive gear set includes a first bevel gear fordriving the first geartrain and the second drive gear set includes asecond bevel gear for driving the second geartrain, wherein the firstbevel gear defines a first inclusive angle between the first side andthe first drive axis and the second bevel gear defines a secondinclusive angle between the second side and the second drive axis.

In a further embodiment of any of the foregoing accessory systemembodiments, the first inclusive angle is independent of the secondinclusive angle.

In a further embodiment of any of the foregoing accessory systemembodiments, including a first spur angle between the accessory gearboxaxis and the first drive axis and a second spur angle between theaccessory gearbox axis and the second drive axis.

In a further embodiment of the foregoing accessory system embodimentwhere the first spur angle is independent of the second spur angle.

In a further embodiment of an of the foregoing accessory systemembodiments where a tower shaft drives the driven gear set.

In a further embodiment of any of the foregoing accessory systemembodiments, the driven gear set is removable from the accessory gearboxsuch that the tower shaft is removable through the accessory gearbox.

In a further embodiment of any of the foregoing accessory systemembodiments, the first geartrain drives at least one accessory componentremovably mounted to the first side and the second geartrain drives atleast one accessory component removably mounted to the second side.

In a further embodiment of any of the foregoing accessory systemembodiments, the accessory gearbox includes an aft side transverse tothe first and second sides and an aft geartrain including a shaftrotatable about an axis perpendicular to the aft side, the aft geartraindriven by one of the first and second geartrains for driving at leastone accessory component mounted to the aft side.

A gas turbine engine according to an exemplary embodiment of thisdisclosure, among other possible things, includes an engine case sectiondefined about an engine axis of rotation and an accessory gearbox whichdefines an accessory gearbox axis parallel to the engine axis ofrotation. The accessory gearbox is mounted to the engine case sectionand includes first and second sides, a first geartrain including a firstset of shafts aligned within a first plane transverse to the first sideof the accessory gearbox, a second geartrain within the accessorygearbox including a second set of shafts aligned within a second planetransverse to the second side of the accessory gearbox, a driven gearset defining an input axis, a first drive gear set driven by the drivengear set about a first drive axis for driving the first gear set, thefirst drive gear set including a first bevel gear defining a firstinclusive angle between the first drive axis and the first plane, and asecond drive gear set driven by the driven gear set about a second driveaxis for driving the second gear set, the first drive gear set includingsecond bevel gear defining a second inclusive angle between the seconddrive axis and the second plane.

In a further embodiment of the foregoing gas turbine engine embodiment,the first geartrain drives at least one accessory component removablymounted to the first side and the second geartrain drives at least oneaccessory component removably mounted to the second side.

In a further embodiment of any of the foregoing gas turbine engineembodiments, the first and second drive axes are parallel to the inputaxis.

In a further exemplary embodiment of any of the foregoing gas turbineengine embodiments, a tower shaft drives the driven gear set and isremovable through the accessory gearbox.

An exemplary method of removing a tower shaft of this disclosure, amongother possible things includes the steps of providing an accessorygearbox with first and second driven gear sets disposed parallel to aninput axis of a tower shaft, removing a gear for driving both of thefirst and second driven gear sets mounted to the tower shaft, and movingthe tower shaft through the accessory gearbox past the first and seconddriven gear sets.

In a further exemplary embodiment of the foregoing method, a couplershaft supported within the accessory gearbox coupled to the tower shaftis removed.

Although the different examples have the specific components shown inthe illustrations, embodiments of this invention are not limited tothose particular combinations. It is possible to use some of thecomponents or features from one of the examples in combination withfeatures or components from another one of the examples.

These and other features disclosed herein can be best understood fromthe following specification and drawings, the following of which is abrief description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a general sectional view through an embodiment of a gasturbine engine along the engine longitudinal axis.

FIG. 2 is a general partial sectional view through an embodiment of agas turbine engine along the engine longitudinal axis.

FIG. 3 is a bottom view of an example accessory system for a gas turbineengine.

FIG. 4 is a top view of an example accessory gearbox for a gas turbineengine.

FIG. 5 is a front view of the example accessory gearbox.

FIG. 6 is a schematic representation of a geartrain of the exampleaccessory gearbox.

FIG. 7 is a partial exploded view of the accessory gearbox illustratingan example method of removing a towershaft.

DETAILED DESCRIPTION

FIG. 1 illustrates a general partial fragmentary schematic view of anembodiment of a gas turbine engine 10 suspended from an engine pylon Pwithin an engine nacelle assembly N as is typical of an aircraftdesigned for subsonic operation. The engine pylon P or other supportstructure is typically mounted to an aircraft wing W; however, theengine pylon P may alternatively extend from other aircraft structuresuch as an aircraft empennage.

The gas turbine engine 10 includes a core engine C within a core nacelle12 that houses a low spool 14 and high spool 24. The low spool 14includes a low pressure compressor 16 and low pressure turbine 18. Thelow spool 14 may drive a fan section 20 either directly or through agear train 22. The high spool 24 includes a high pressure compressor 26and high pressure turbine 28. A combustor 30 is arranged between thehigh pressure compressor 26 and high pressure turbine 28. The low andhigh spools 14, 24 rotate about an engine axis of rotation A.

The engine 10 in the disclosed embodiment is a high-bypass gearedarchitecture aircraft engine. In one disclosed embodiment, the engine 10bypass ratio is greater than ten (10:1), the turbofan diameter issignificantly larger than that of the low pressure compressor 16, andthe low pressure turbine 18 has a pressure ratio that is greater than5:1. The gear train 22 may be an epicycle gear train such as a planetarygear system or other gear system with a gear reduction ratio of greaterthan 2.5:1. It should be understood, however, that the above parametersare only exemplary of one embodiment of a geared architecture engine andthat the present application is applicable to other gas turbine enginesincluding direct drive turbofans.

Airflow enters a fan nacelle 34, which at least partially surrounds thecore nacelle 12. The fan section 20 communicates airflow into the corenacelle 12 to power the low pressure compressor 16 and the high pressurecompressor 26. Core airflow compressed by the low pressure compressor 16and the high pressure compressor 26 is mixed with the fuel in thecombustor 30 and expanded over the high pressure turbine 28 and lowpressure turbine 18. The turbines 28, 18 are coupled for rotation with,respective, spools 24, 14 to rotationally drive the compressors 26, 16and, through the optional gear train 22, the fan section 20 in responseto the expansion. A core engine exhaust exits the core nacelle 12through a core nozzle 38 defined between the core nacelle 12 and a tailcone 32.

A bypass flow path is defined between the core nacelle 12 and the fannacelle 34. The engine 10 generates a high bypass flow arrangement witha bypass ratio in which approximately 80 percent or more of the airflowentering the fan nacelle 34 becomes bypass flow. The bypass flowcommunicates through the generally annular bypass flow path.

Referring to FIG. 2, engine static structure 42 includes sub-structuressuch as a core engine case structure 44 often referred to as the enginebackbone. The engine case structure 44 generally includes a fan case 46,an intermediate case (IMC) 48, a high pressure compressor case 50, adiffuser case 52, a low pressure turbine case 54, and a turbine exhaustcase 56. The core engine case structure 44 is secured to the fan case 46at the IMC 48 which includes a multiple of circumferentially spacedradially extending fan exit guide vanes (FEGVs) 36.

An accessory gearbox 60 is mounted to the case structure 44 generallyparallel to the engine axis of rotation A. The accessory gearbox 60takes advantage of the significant axial area within the core nacelle 12(FIG. 1) to support an engine accessory system 62 which may includeaccessory components (AC) such as an Air Turbine Starter (ATS), adeoiler (D), a hydraulic pump (HP), an oil pump (OP), an integrateddrive generator (IDG), a permanent magnet alternator (PMA), a fuel pumpmodule (FPM), and others (FIG. 3). It should be understood, that anynumber and type of accessory components AC may alternatively oradditionally be provided.

Referring to FIG. 3, the accessory gearbox 60 includes a first geartrain82 and a second geartrain 84 driven by corresponding first and seconddriven gear sets 78, 80. The first geartrain 82 includes shaftsrotatable about axes perpendicular to a first side 64. The secondgeartrain 84 includes shafts rotatable about axes perpendicular to asecond side 66. The first and second drive gear sets 78, 80 are drivenby a driven gear set 86 that rotates about an input axis T.

Accessory components are removably mounted to one of the first andsecond sides 64, 66 and driven by the corresponding one of thegeartrains 82, 84. In this example, the first geartrain 82 drives theFPM and HP, and the second geartrain 84 drives the ATS and IDG. Theexample accessory gearbox 60 further includes an aft side 68 thatsupports a removably mounted OP.

Each of the first and second sides is disposed parallel to the engineaxis A and adjacent the engine case structure 44. The parallel andadjacent mounting provides for reductions to component removal envelops.Moreover, the disclosed mounting provides more efficient supply conduitattachment and routing. Although a specific example is disclosed anddescribed, different components and position are within thecontemplation of this disclosure.

Referring to FIGS. 4, 5 and 6, the accessory gearbox 60 providesflexibility in design by removing constraints necessitated by the use ofthree-way bevel gearing arrangements in previous accessory gearboxes.The example accessory gearbox 60 includes the first and second drivengear sets 78, 80 that rotate about corresponding first and second driveaxes 90, 88 parallel to the input axis T. Each of the first and seconddriven gear sets 78, 80 in turn drive a corresponding one of the firstand second geartrains 82, 84.

The example accessory gearbox 60 provides for the adaptation to spaceconstraints by providing for independent adjustment and configurationdue at least in part to the use of independent bevel gear sets.Accordingly, an inclusive angle 96 between the second drive axis 88,axis 73 and a second plane 92 (best shown in FIG. 5) intersecting gearsof the second geartrain 84 is independent of an inclusive angle 98between the first drive axis 90, axis 75 and a first plane 94 (bestshown in FIG. 5) intersecting gears of the first geartrain 82. The firstplane 94 intersects each of the gears of the first geartrain 82 and theaxis 75 about which shaft 72 rotates. The second plane 92 intersectseach of the gears of the second geartrain 84 and the axis 73 about whichshaft 74 rotates. The inclusive angles 98 and 96 are a function of theconfiguration of first and second driven bevel gears 118, 120. Becausethe driven bevel gears 118, 120 are of a 2-way configuration, the angleof one does not dictate the angle of the other. Accordingly, theinclusive angles 96 and 98 may be different, and are not dependent oneach other.

Each of the first and second drive gear sets 78, 80 includes a drivespur gear 140, 116 that is driven by a tower shaft spur gear 110 drivenby the tower shaft 117. The first and second drive gear sets 78, 80rotate about the axes 90, 88 parallel to the input axis T. First andsecond spur angles 106 and 104 are also independent of each other andprovide for varied placement and alignment of the correspondinggeartrains 82, 84. The example spur angle is that angle between thegearbox axis GB and a plane defined between the input axis T and thecorresponding one of the first and second drive axes 90, 88. In thisexample the first and second spur angles 106 and 104 are the same;however, these angles can be adjusted to conform the example accessorygearbox 60 to a desired installation space.

A first geartrain angle 102 is defined between the first plane 94 of thefirst geartrain 78 and a plane extending between the first drive axis 90and the axis 75 of the shaft 72 in the first geartrain 82 that includesthe bevel gear 124. A second geartrain angle 100 is defined between thesecond plane 92 of the second geartrain 84 and a plane extending betweenthe second axis 88 and the axis 73 of a shaft 74 in the second geartrain84. The first and second geartrain angles 102, 100 are independent ofeach other and therefore provide further gearbox adaptation flexibility.

The second driven bevel gear 120 is mated with bevel gear 122 thatdrives the shaft 74 of the second geartrain 84. The second drive bevelgear 120 and the bevel gear 122 are sized to provide a desired inputspeed of the ATS along with defining the inclusive angle 96. An ATS spurgear 126 is supported on the shaft 74 along with the bevel gear 122 todrive the IDG spur 128 gear supported on shaft 76. The gear ratiobetween the IDG spur gear 128 and the ATS spur gear 126 provides thedesired input speed for the IDG.

The first driven bevel gear 118 drives the FPM bevel gear 124 at adesired speed for the FPM. Because the geartrains 82, 84 are driven byindependent first and second drive gear sets 78, 80, the first drivencomponent of each geartrain 82, 84 can be driven at different speeds. Inthis example, the shaft 72 supports the FPM bevel gear 124 and an FPMspur gear 130. The FPM spur gear 130 in turn drives an HP spur gear 132supported on shaft 70. The shaft 70 further supports the HP bevel gear134 that drives the OP bevel gear 136 that drives the OP supported onthe aft side 68. It should be understood, that the specific features ofthe exemplary gearbox 60 may be modified to support and drive variousother accessory components.

Referring to FIG. 7, the example gearbox 60 provides for the removal ofthe engine tower shaft 117 without removal of the gearbox 60. In thisexample, the towershaft 117 is removable through the gearbox 60. Removalis facilitated by removing a tower shaft cover 115, tower shaft bearing112, tower shaft spur gear 110 and a coupler shaft 108. Once thesefeatures are removed, the tower shaft 117 can be removed through theaccessory gearbox 60. The input axis T is disposed at an angle 138relative to the gearbox axis GB. The front portion of the examplegearbox 60 is angled to accommodate the angle 138 thereby providing aslimmer forward profile. Moreover, separation of the bevel gears fromthe tower shaft 117 as is provided by the parallel first and seconddriven gear sets 78, 80 simplifies removal by eliminating anyrequirement to remove portions of the geartrains 82, 84.

Variations of the disclosed accessory gearbox 60 are possible whilemaintaining the configuration of the first and second drive spur gears140, 116 and modification to the drive bevel gears 118 and 120 toaccommodate the requirements of individual applications.

Although an example embodiment has been disclosed, a worker of ordinaryskill in this art would recognize that certain modifications would comewithin the scope of this disclosure. For that reason, the followingclaims should be studied to determine the scope and content of thisinvention.

What is claimed is:
 1. A method of removing a tower shaft of a gasturbine engine comprising: providing an accessory gearbox with first andsecond driven gear sets disposed parallel to an input axis of a towershaft; removing a gear for driving both of the first and second drivengear sets mounted to the tower shaft; moving the tower shaft through theaccessory gearbox past the first and second driven gear sets; andmaintaining the first and second driven gear sets within the accessorygearbox while removing the tower shaft.
 2. The method of removing atower shaft of a gas turbine engine as recited in claim 1, including thestep of removing a coupler shaft supported within the accessory gearboxcoupled to the tower shaft.
 3. The method of removing a tower shaft of agas turbine engine as recited in claim 1, including removing a coverover an opening defined in the accessory gear box aligned with an axisof rotation of the tower shaft and removing a tower shaft bearingsupporting rotation of the tower shaft through the opening.
 4. Themethod of removing a tower shaft of a gas turbine engine as recited inclaim 1, wherein the tower shaft is disposed along the input axis thatis angled relative to a gearbox axis and the accessory gearbox and anopening through which the tower shaft is removed is disposed along theinput axis.
 5. The method of removing a tower shaft of a gas turbineengine as recited in claim 3, including removing the gear for drivingboth the first and second driven gear sets through the opening.
 6. Themethod of removing a tower shaft of a gas turbine engine as recited inclaim 4, wherein moving the tower shaft comprises moving the tower shaftaxially along the axis of rotation through the accessory gearbox and outthe opening.
 7. The method of removing a tower shaft of a gas turbineengine as recited in claim 1, the first driven gear set is disposedabout a first drive axis and the second driven gear set is disposedabout a second drive axis parallel to the input axis and remain withinthe accessory gear box upon removal of the gear.
 8. The method ofremoving a tower shaft of a gas turbine engine as recited in claim 1,wherein the first driven gear set comprises a first spur gear, thesecond driven gear set comprises a second spur gear, and the gearcomprises a drive spur gear driving the first and second spur gears. 9.A method of removing a tower shaft of a gas turbine engine comprising:providing an accessory gearbox with first and second driven gear setsdisposed parallel to an input axis of a tower shaft, wherein the towershaft is disposed along the input axis that is angled relative to agearbox axis; removing a gear for driving both of the first and seconddriven gear sets mounted to the tower shaft; and moving the tower shaftthrough an opening in the accessory gearbox disposed along the inputaxis past the first and second driven gear sets.
 10. The method ofremoving a tower shaft of a gas turbine engine as recited in claim 9,including removing the gear for driving both the first and second drivengear sets through the opening.
 11. The method of removing a tower shaftof a gas turbine engine as recited in claim 10, the first driven gearset is disposed about a first drive axis and the second driven gear setis disposed about a second drive axis parallel to the input axis andremain within the accessory gear box upon removal of the gear.
 12. Amethod of removing a tower shaft of a gas turbine engine comprising:providing an accessory gearbox with first and second driven gear setsdisposed parallel to an input axis of a tower shaft; removing a gear fordriving both of the first and second driven gear sets mounted to thetower shaft, the first driven gear set is disposed about a first driveaxis and the second driven gear set is disposed about a second driveaxis parallel to the input axis; moving the tower shaft through theaccessory gearbox past the first and second driven gear sets wherein thefirst and second driven gear sets remain within the accessory gear boxupon removal of the gear.
 13. The method of removing a tower shaft of agas turbine engine as recited in claim 12, including the step ofremoving a coupler shaft supported within the accessory gearbox coupledto the tower shaft.
 14. The method of removing a tower shaft of a gasturbine engine as recited in claim 13, including removing a cover overan opening defined in the accessory gear box aligned with an axis ofrotation of the tower shaft and removing a tower shaft bearingsupporting rotation of the tower shaft through the opening.
 15. Themethod of removing a tower shaft of a gas turbine engine as recited inclaim 14, wherein the tower shaft is disposed along the input axis thatis angled relative to a gearbox axis and the accessory gearbox and theopening through which the tower shaft is removed is disposed along theinput axis.